CVE-2026-5740— Unauthenticated WebSocket binary frame causes denial of service in Mattermost Server
Possible ATT&CK Techniques 1AI
T1499 · Endpoint Denial of ServiceAffected Version Matrix 9
| Vendor | Product | Version Range | Status |
|---|---|---|---|
| Mattermost | Mattermost | 11.6.0≤ 11.6.0 | affected |
11.5.0≤ 11.5.3 | affected | ||
11.4.0≤ 11.4.4 | affected | ||
10.11.0≤ 10.11.14 | affected | ||
11.7.0 | unaffected | ||
11.6.1 | unaffected | ||
11.5.4 | unaffected | ||
11.4.5 | unaffected | ||
| … +1 more rows | |||
Get alerts for future matching vulnerabilitiesLog in to subscribe
I. Basic Information for CVE-2026-5740
Vulnerability Information
Have questions about the vulnerability? See if Shenlong's analysis helps!
View Shenlong Deep Dive ↗ Although we use advanced large model technology, its output may still contain inaccurate or outdated information.Shenlong tries to ensure data accuracy, but please verify and judge based on the actual situation.
Vulnerability Title
Unauthenticated WebSocket binary frame causes denial of service in Mattermost Server
Source: NVD (National Vulnerability Database)
Vulnerability Description
Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to properly validate msgpack-encoded WebSocket frames before memory allocation which allows an unauthenticated remote attacker to crash the server process and cause a full service outage for all users via a crafted binary WebSocket message sent to the public WebSocket endpoint.. Mattermost Advisory ID: MMSA-2026-00647
Source: NVD (National Vulnerability Database)
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: NVD (National Vulnerability Database)
Vulnerability Type
未经控制的内存分配
Source: NVD (National Vulnerability Database)
Affected Products
| Vendor | Product | Affected Versions | CPE | Subscribe |
|---|---|---|---|---|
| Mattermost | Mattermost | 11.6.0 ~ 11.6.0 | - |
II. Public POCs for CVE-2026-5740
| # | POC Description | Source Link | Shenlong Link |
|---|
AI-Generated POCPremium
No public POC found.
Login to generate AI POCIII. Intelligence Information for CVE-2026-5740
请登录查看更多情报信息。
Same Patch Batch · Mattermost · 2026-05-22 · 8 CVEs total
| CVE-2026-4635 | 6.5 MEDIUM | Persistent notification timing attack causing server denial of service |
| CVE-2026-5755 | 6.5 MEDIUM | Denial of service via crafted TIFF file upload |
| CVE-2026-3473 | 5.9 MEDIUM | Improper file ownership validation in the Boards API allows unauthorised file access |
| CVE-2026-28735 | 5.4 MEDIUM | GitHub OAuth Scope Validation |
| CVE-2026-5308 | 4.9 MEDIUM | Missing request body size limits on Zoom plugin HTTP endpoints |
| CVE-2026-4646 | 4.3 MEDIUM | Insufficient input validation in GitHub plugin API causes denial of service |
| CVE-2026-3636 | 4.3 MEDIUM | Sanitize team member data returned by API |
IV. Related Vulnerabilities
Same product: Mattermost
- CVE-2026-28735
GitHub OAuth Scope Validation - CVE-2026-4635
Persistent notification timing attack causing server denial - CVE-2026-3473
Improper file ownership validation in the Boards API allows - CVE-2026-4646
Insufficient input validation in GitHub plugin API causes de - CVE-2026-3636
Sanitize team member data returned by API
Same vendor: Mattermost
- CVE-2026-28735
GitHub OAuth Scope Validation - CVE-2026-4635
Persistent notification timing attack causing server denial - CVE-2026-3473
Improper file ownership validation in the Boards API allows - CVE-2026-4646
Insufficient input validation in GitHub plugin API causes de - CVE-2026-3636
Sanitize team member data returned by API
Same weakness: CWE-789
- CVE-2026-8485
Uncontrolled Memory Allocation vulnerability in Progress Sof - CVE-2026-47313
SAMSUNG Escargot 安全漏洞 - CVE-2026-6340
Memory Exhaustion via Malicious 7zip File Upload - CVE-2021-47973
Sticky Notes Widget 3.0.6 Denial of Service via Buffer Overf - CVE-2021-47972
Sticky Notes & Color Widgets 1.4.2 Denial of Service
V. Comments for CVE-2026-5740
No comments yet